Perspective on Fusion Research,
Development Pathways, and
Applications
Mohamed Abdou
Distinguished Professor of Engineering and Applied Science
Director, Center for Energy Science and Technology Advanced Research
Director, Fusion Science and Technology Center
University of California-Los Angeles (UCLA)
Plenary Lecture at ISEM 2009 14th International Symposium on Applied
Electromagnetics and Mechanics, Xi’an, China, September 23, 2009
1
Perspective on Fusion Research,
Development Pathways, and Applications
OUTLINE
•
•
•
•
•
•
•
•
•
Fusion Research Transition to Fusion Science and Engineering
DEMO Goal
ITER
Blanket Principles and Interactions
MHD Thermofluid Issues
Blanket Types and Issues
Blanket Testing in ITER
Need for a New Fusion Nuclear Facility
Summary of Key Magnetoscience Issues in Magnetic Fusion
Energy Systems
• Summary
2
2
What is fusion?
 Two light nuclei combining to form a heavier nuclei
(the opposite of nuclear fission). Fusion powers the Sun and Stars.
Deuterium
mc2
E=
17.6 MeV
Tritium
Neutron
80% of energy
release
(14.1 MeV)
Used to breed
tritium and close
the DT fuel cycle
Li + n → T + He
Li in some form must be
used in the fusion
system
Helium
20% of energy release
(3.5 MeV)
Illustration from DOE brochure
 Deuterium and tritium is the easiest,
attainable at lower plasma temperature,
because it has the largest reaction
rate and high Q value.
 The World Program is focused
on the D-T Cycle.
3
077-05/rs
3
Incentives for Developing Fusion
 Sustainable energy source
(for DT cycle: provided that Breeding Blankets are
successfully developed and tritium self-sufficiency
conditions are satisfied)
 No emission of Greenhouse or other polluting gases
 No risk of a severe accident
 No long-lived radioactive waste
Fusion energy can be used to produce electricity
and hydrogen, and for desalination.
4
Fusion Research is about to transition from Plasma
Physics to Fusion Science and Engineering
• 1950-2010
– The Physics of Plasmas
• 2010-2035
– The Physics of Fusion
– Fusion Plasmas-heated and sustained
• Q = (Ef / Einput )~10
• ITER (magnetic fusion) and NIF (inertial fusion)
• 2010-2040 ?
– Fusion Nuclear Science and Technology for Fusion
• > 2050 ?
– DEMO by 2050?
– Large scale deployment > 2050!
5
The World Fusion Program has a Goal for a
Demonstration Power Plant (DEMO) by ~2040(?)
Plans for DEMO are based on Tokamaks
Poloidal Ring Coil
Cryostat
Coil Gap
Rib Panel
Blanket
Maint.
Port
Plasma
Vacuum
Vessel
Center Solenoid Coil
Toroidal Coil
(Illustration is from JAEA DEMO Design)
6
ITER
• The World has started construction of the next
step in fusion development, a device called ITER.
• ITER will demonstrate the scientific and
technological feasibility of fusion energy for
peaceful purposes.
• ITER will produce 500 MW of fusion power.
• Cost, including R&D, is ~15 billion dollars.
•
ITER is a collaborative effort among Europe, Japan,
US, Russia, China, South Korea, and India. ITER
construction site is Cadarache, France.
• ITER will begin operation in hydrogen in ~2019. First D-T
Burning Plasma in ITER in ~ 2026.
7
ITER is a reactor-grade tokamak plasma physics
experiment - A huge step toward fusion energy






Will use D-T and produce neutrons
500MW fusion power, Q=10
Burn times of 400s
Reactor scale dimensions
Actively cooled PFCs
Superconducting magnets
~29 m
~15 m
By Comparison,
JET
 ~10 MW
 ~1 sec
 Passively
Cooled
JET
ITER
8
Magnet System in Tokamak (e.g. ITER) has 4 sets of coils
• 18 Toroidal Field (TF) coils
produce the toroidal magnetic
field to confine and stabilize
the plasma
− Superconducting,
Nb3Sn/Cu/SS
− Max. field: 11.8T
• 6 Poloidal Field (PF) coils
position and shape the
plasma
− Superconducting,
NbTi/Cu/SS
− Max. field: 6T
• Central Solenoid (CS)
coil induces current in
the plasma
• 18 Correction coils correct error fields
− Superconducting, NbTi/Cu/SS
− Max. field < 6T
TF coil case provides main
structure of the magnet
system and machine core
− Superconducting,
Nb3Sn/Cu/alloy908
−Max. field: 13.5T
Stored energy in ITER magnetic field is large ~ 1200 MJ
Equivalent to a fully loaded 747 moving at take off speed 265 km/h
9
New Long-Pulse Confinement and Other Facilities
Worldwide will Complement ITER
Japan (w/EU)
China
EAST
JT-60SA
(also LHD)
Europe
South Korea
W7-X
(also
JT-60SA)
India
SST-1
ITER Operations:
34% Europe
13% Japan
13% U.S.
10% China
10% India
10% Russia
10% S. Korea
KSTAR
U.S.
Being planned
Fusion Nuclear Science
&Technology Testing
Facility
(FNSF/CTF/VNS)
The primary functions of the blanket are to provide for:
Power Extraction & Tritium Breeding
Shield
Blanket
Vacuum vessel
Radiation
DT
Plasma
Neutrons
First Wall
Tritium breeding zone
Coolant for energy
extraction
Magnets
Lithium-containing Liquid metals (Li, PbLi) are strong candidates as
breeder/coolant.
11
Fusion Nuclear Science and Technology (FNST)
Fusion Power & Fuel Cycle Technology
FNST includes the scientific issues and
technical disciplines as well as materials,
engineering and development of fusion
nuclear components:
From the edge of Plasma to TF Coils:
1. Blanket Components (includ. FW)
2. Plasma Interactive and High Heat Flux
Components (divertor, limiter, rf/PFC element, etc)
3. Vacuum Vessel & Shield Components
The location of the Blanket inside the
vacuum vessel is necessary but has
major consequences:
a- many failures (e.g. coolant leak)
require immediate shutdown
b- repair/replacement take long time
12
All Nuclear Responses (e.g. tritium production and Radiation
Damage Parameters) have Steep Gradients in the Blanket
3.0 10-8
103
Damage Rate in Steel Structure per FPY
Tritium Production Rate (kg/m 3.s)
Radial Distribution of Damage Rate
in Steel Structure
2.5 10-8
2.0 10-8
Radial Distribution of Tritium Production
in LiPb Breeder
2
Neutron Wall Loading 0.78 MW/m
1.5 10-8
DCLL TBM
LiPb/He/FS
90% Li-6
1.0 10-8
5.0 10-9
0
0.0 10
0
Front
Channel
10
5
20
102
DCLL TBM
LiPb/He/FS
90% Li-6
101
100
dpa/FPY
He appm/FPY
H appm/FPY
Back Channel
15
2
Neutron Wall Loading 0.78 MW/m
25
Radial Distance from FW (cm)
Radial variation of tritium production rate in LiPb
in the DCLL TBM (Linear Scale)
30
10-1
0
5
10
15
20
25
30
35
40
Depth in Blanket (cm)
Radial variation of damage parameters in the ferritic
steel structure of the DCLL TBM (Log-Scale)
14
Fusion environment is unique and complex:
multi-component fields with gradients
•Neutron and Gamma fluxes
•Particle fluxes
•Heat sources (magnitude and gradient)
– Surface (from plasma radiation)
– Bulk (from neutrons and gammas)
• Magnetic Field (3-component)
– Steady field
– Time varying field
• With gradients in magnitude and direction
Plasma
Width
B
0
(for ST)
BT
Inner
Edge
Bp
Outer
Edge
R
Multi-function blanket in multi-component field environment leads to:
- Multi-Physics, Multi-Scale Phenomena
Rich Science to Study
15
- Synergistic effects that cannot be anticipated from simulations & separate effects
tests. Modeling and Experiments are challenging.
Challenging
Fusion Nuclear Science & Technology Issues
1. Tritium Supply &
Tritium Self-Sufficiency
2. High Power Density
3. High Temperature
4. MHD for Liquid Breeders / Coolants
5. Tritium Control (Extraction and Permeation)
6. Reliability / Maintainability / Availability
7. Testing in Fusion Facilities
16
Flows of electrically conducting coolants will experience
complicated MHD effects in the magnetic fusion environment
3-component magnetic field and complex geometry
– Motion of a conductor in a magnetic field produces an EMF that can
induce current in the liquid. This must be added to Ohm’s law:
j   (E  V  B )
– Any induced current in the liquid results in an additional body force
in the liquid that usually opposes the motion. This body force must
be included in the Navier-Stokes equation of motion:
V
1
1
 (V  )V   p   2 V  g  j  B
t


– For liquid metal coolant, this body force can have dramatic impact
on the flow: e.g. enormous MHD drag, highly distorted velocity
profiles, non-uniform flow distribution, modified or suppressed
turbulent fluctuations.
Dominant impact on LM design.
Challenging Numerical/Computational/Experimental Issues
17
MHD Characteristics of Fusion
Liquid Breeder Blanket Systems
18
A perfectly insulated “WALL”
can solve the problem, but is it
practical?
Self-Cooled liquid Metal
Blankets are NOT feasible now
because of MHD Pressure Drop.
Conducting walls
Insulated walls
Lines of current enter the low
resistance wall – leads to very
high induced current and high
pressure drop
1
0.8
0.6
0.4
1
0.8
0.6
0.4
0.2
0.2
0
0
-0.2
-0.2
All current must close in the
liquid near the wall – net drag
from jxB force is zero
-0.4
-0.6
-0.8
-0.4
-0.6
-0.8
-1
-1
-1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Net JxB body force
p = VB2 tw w/a
- For high magnetic field and high
speed (self-cooled LM concepts in
inboard region) the pressure drop
is large
- The resulting stresses on the wall
exceed the allowable stress for
candidate structural materials
•
-
•
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Perfect insulators make the net
MHD body force zero
But insulator coating crack
tolerance is very low (~10-7).
–
•
-0.8
It appears impossible to develop
practical insulators under fusion
environment conditions with large
temperature, stress, and radiation
gradients
Self-healing coatings have been
proposed but none has yet been
found (research is on-going)
19
Impact of MHD and no practical Insulators: No self-cooled blanket option
Separately-cooled LM Blanket
Example: PbLi Breeder / Helium Coolant with RAFM
Module box
 EU mainline blanket design
(container & surface
 All energy removed by separate
heat flux extraction)
Helium coolant
 The idea is to avoid MHD issues
But, PbLi must still be circulated to extract
tritium
Breeder cooling
unit (heat extraction
from PbLi)
 ISSUES:
– Low velocity of PbLi leads to high
tritium partial pressure, which leads to
tritium permeation (Serious Problem)
– Tout limited by PbLi compatibility with
RAFM steel structure ~ 470 C
(and also by limit on Ferritic, ~550 C)
 Possible MHD Issues :
– MHD pressure drop in the inlet
manifolds
– B- Effect of MHD buoyancy-driven flows
on tritium transport
Stiffening structure
Drawbacks: Tritium
Permeation and limited
thermal efficiency
(resistance to accidental in-box
pressurization i.e He leakage)
He collector system
(back)
20
Pathway Toward Higher Temperature through Innovative
Designs with Current Structural Material (Ferritic Steel):
Dual Coolant Lead-Lithium (DCLL) FW/Blanket Concept
 First wall and ferritic steel structure
cooled with helium
 Breeding zone is self-cooled
 Structure and Breeding zone are
separated by SiCf/SiC composite
flow channel inserts (FCIs) that:
 Provide thermal insulation to
decouple PbLi bulk flow
temperature from ferritic steel
wall
 Provide electrical insulation to
reduce MHD pressure drop in
the flowing breeding zone
DCLL Typical Unit Cell
FCI does not serve structural function
Pb-17Li exit temperature can be significantly higher than the
operating temperature of the steel structure  High Efficiency
21
High pressure drop is only one of the MHD issues for
LM blankets; MHD heat and mass transfer are also of
great importance!
Instabilities and 3D MHD effects in complex
detailed geometry and configuration with
magnetic and nuclear fields gradients have
major impact:
FCI overlap gaps act
as conducting breaks
in FCI insulation
• Unbalanced pressure drops (e.g. from
insulator cracks) leading to flow control and
channel stagnation issues
• Unique MHD velocity profiles and instabilities
affecting transport of mass and energy.
Accurate Prediction of MHD Heat &Mass
Transfer is essential to addressing
important issues such as:
• thermal stresses,
• temperature limits,
• failure modes for structural and
functional materials,
• thermal efficiency, and
• tritium permeation.
and hence disturb current
flow and velocity, and
redistribute energy
Courtesy of Munipalli et al.
(Ha=1000; Re=1000; =5 S/m,
cross-sectional dimension expanded 10x)
077-05/rs
22
Buoyancy effects in DCLL blanket
DCLL DEMO blanket, US
 Exp(r )
q(r )  qmax
 a 2
qmax
and associated T 
~ 103 K
k
Caused by
Can be 2-3 times stronger than
forced flows. Forced flow: 10 cm/s.
Buoyant flow: 25-30 cm/s.
 exp{ r}
q(r ) ~ qmax
In buoyancy-assisted (upward)
flows, buoyancy effects may play a
positive role due to the velocity jet
near the “hot” wall, reducing the
FCI T.
In buoyancy-opposed (downward)
flows, the effect may be negative
due to recirculation flows.
Effect on the interface T, FCI T,
heat losses, tritium transport.
Vorticity distribution in the buoyancy-assisted
(upward) poloidal flow
23
Corrosion Is A Serious Issue For LM Blankets
•
At present, the interface temperature between PbLi and Ferritic Steel (FS) is
limited to < 470 C because of corrosion.
– This is very restrictive and does not allow higher temperature operation with FS or
advanced ODS.
•
Data available are from corrosion experiments with no magnetic field. They
are static or dynamic.
– Results show strong dependence on temperature and on the velocity of PbLi.
– Therefore, corrosion should be expected to experience MHD effects due to sharp
changes in the velocity and temperature profiles.
– There is experimental evidence of the effect of magnetic field.
•
Criteria for determining the allowable interface temperature :
a) Thinning of the walls (in the “hot” section) due to corrosion
b) Deposition of the corrosion products transported in the heat transport loop to the Heat
Exchanger (“cold” section) causing radioactive “CRUD” that hampers HX maintenance.
c) Corrosion products deposition in the “cold” section causing clogging small orifices,
valves, etc.
Usually the criterion c) is applied with the assumption, that the corrosion rate has to be limited to 20
micron/year in order to avoid clogging. This leads to an allowable interface temperature of ~ 470 C as
measured in experiments with turbulent flow without magnetic fields
•
Experiments with sodium loops have shown that deposits in the "cold"
sections is more limiting than thinning of the "hot" walls.
Hence, in addition to corrosion rates, it is important to predict the behavior of the
corrosion products in the entire heat transport loop, particularly “deposition”.
24
Experiments in Riga (funded by Euratom)
Show Strong Effect of the Magnetic Field on Corrosion
(Results for PbLi in Ferritic Steel)
Macrostructure of the washed samples
after contact with the PbLi flow
B=0 T
B=1.8 T
From: F. Muktepavela et al. EXPERIMENTAL STUDIES
OF THE STRONG MAGNETIC FIELD ACTION ON
THE CORROSION OF RAFM STEELS IN Pb17Li MELT
FLOWS, PAMIR 7, 2008
Strong experimental evidence of
significant effect of the applied magnetic
field on corrosion rate. The underlying
physical mechanism has not been fully
understood yet.
25
Need R&D on Corrosion: Modelling and Experiments in
MHD Flows Relevant to the Fusion System Environment
•
Corrosion includes many physical mechanisms that are currently not well
understood (dissolution of the metals in the liquid phase, chemical reactions of dissolved
non-metallic impurities with solid material, transfer of corrosion products due to convection
and thermal and concentration gradients, etc.).
•
•
We need to better understand corrosion process, including transport and
deposition.
We need new models that can predict corrosion rates and transport and
deposition of corrosion products throughout the heat transport system.
– These models need to account for MHD velocity profiles and heat transfer in the
blanket and the temperature gradients and complex geometry in the entire heat
transport systems.
•
More comprehensive experiments are needed:
– Need to simulate MHD velocity profiles
– Need to simulate the temperature field and temperature gradients in the “hot” and
“cold” sections.
– Better instrumentation.
•
•
R&D to develop corrosion resistant “barriers” will have high pay off.
Highest interest is in PbLi systems with both ferritic steel and SiC (FCI).
26
Illustration of Coupling between MHD and
heat and mass transfer in blanket flows
MHD Flow
Heat Transfer
Convection
He
Bubbles
formation
and their
transport
Mass Transfer
Buoyanoydriven flows
Diffusion
Dissolution, convection,
and diffusion through
the liquid
Tritium
transport
Dissolution and
diffusion through the
solid
Tritium Permeation
Corrosion
Transport of
corrosion
products
Deposition and
aggregation
Interfacial
phenomena
Coupling through the source / sink term, boundary conditions, and transport coefficients
27
Testing Blankets in the fusion environment is Necessary: Combined effects
of Radiation, Surface Heat flux, Nuclear Heating & gradients, Magnetic
field & gradients, etc can be reproduced only in a fusion facility.
Example: MHD flow & FCI behavior are highly coupled in a complex fusion environment.
 PbLi flow is strongly influenced by MHD interaction
with plasma confinement field and buoyancy-driven
convection driven by spatially non-uniform
volumetric nuclear heating.
 This MHD flow and convective heat
transport processes determine the
temperature and thermal stress of SiC FCI.
 The FCI temperature and thermal stress coupled
with early-life radiation damage effects in ceramics
affect deformation, cracking, and properties of the
FCI.
Courtesy of S.
Smolentsev
FCI temperature, stress and
deformation
 Cracking and movement of the FCIs will strongly
influence MHD flow behavior by opening up new
conduction paths that change electric current
profiles.
Resulting temperature field also strongly couples to phenomena
such as tritium transport and permeation, and corrosion.
28
28
077-05/rs
28
The issue of external tritium supply is serious and has major
implications on FNST (and Fusion) Development Pathway
Tritium Consumption in Fusion is HUGE! Unprecedented!
55.6 kg per 1000 MW fusion power per year
Production in fission is much smaller & Cost is very high:
Fission reactors: 2–3 kg/year
$84M-$130M/kg (per DOE Inspector General*)
Tritium decays at
5.47% per year
CANDU
Supply
w/o Fusion
*www.ig.energy.gov/documents/CalendarYear2003/ig-0632.pdf
CANDU Reactors: 27 kg from over 40 years,
$30M/kg (current)
Tritium Decays at 5.47% per year
•
A Successful ITER will exhaust most
of the world supply of tritium. Delays in
ITER schedule makes it worse.
•
No DT fusion devices with fusion
power >50 MW, other than ITER, can be
operated without a verified breeding blanket
technology.
•
Development of breeding blanket
technology must be in small fusion power
devices.
With ITER:
2016 1st Plasma,
4 yr. HH/DD
Two Issues In Building A DEMO:
1 – Need Initial (startup) inventory of >10 Kg per DEMO
(How many DEMOS will the world build? And where will startup tritium come from?)
2 – Need Verified Breeding Blanket Technology to install on DEMO
29
Science-Based Framework for FNST R&D involves modeling
and experiments in non-fusion and fusion facilities
Theory/Modeling/Data
Basic
Separate
Effects
Property
Measurement
Multiple
Interactions
Design Codes
Partially
Integrated
Phenomena Exploration
Integrated
Component
•Fusion Env. Exploration Design
Verification &
•Concept Screening
•Performance Verification Reliability Data
Non-Fusion Facilities
(non neutron test stands,
fission reactors and accelerator-based
neutron sources)
Testing in Fusion Facilities
• Experiments in non-fusion facilities are essential and are prerequisites to testing in
fusion facilities.
• Testing in Fusion Facilities is NECESSARY to uncover new phenomena, validate the
science, establish engineering feasibility, and develop components.
30
Three Stages of FNST Testing in Fusion Facilities
Are Required Prior to DEMO
Component Engineering
Development &
Reliability Growth
Fusion “Break-in” &
Scientific Exploration
Engineering Feasibility
& Performance
Verification
Stage I
Stage II
Stage III
1 - 3 MW-y/m2
> 4 - 6 MW-y/m2
0.1 - 0.3 MW-y/m2
 0.5 MW/m2, burn > 200 s
Sub-Modules/Modules
• Initial exploration of coupled
phenomena in fusion
environment
• Screen and narrow blanket design
concepts
1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks
D
E
M
O
1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks
Modules
Modules/Sectors
• Establish engineering feasibility • Failure modes, effects, and rates and
mean time to replace/fix components
of blankets (satisfy basic
(for random failures and planned outage)
functions & performance, up to
10 to 20 % of lifetime)
• Iterative design / test / fail / analyze /
• Select 2 or 3 concepts for further improve programs aimed at reliability
growth and safety
development
• Verify design and predict availability
of FNT components in DEMO
Where to do Stages I, II, and III?
31
ITER Provides Substantial Hardware Capabilities
for Testing of Blanket Systems
TBM System (TBM +
T-Extraction, Heat
Transport/Exchange…)
• ITER has allocated 3
equatorial ports (1.75 x
2.2 m2) for TBM testing
• Each port can
accommodate only 2
modules (i.e. 6 TBMs max)
Bio-shield
He pipes to
TCWS
A PbLi loop Transporter
located in the Port Cell
Area
2.2 m
Equatorial Port Plug
Assy.
Vacuum Vessel
TBM
Assy
Fluence in ITER is limited to 0.3 MW-y/m2. ITER can
only do Stage I. ITER TBM is the most effective and
least expensive to do Stage I. But we need another
facility for Stages II & III.
Port
Frame
32
Fusion Nuclear Science Facility (FNSF)
• The idea of FNSF (also called VNS, CTF) is to build a small size, low
fusion power DT plasma-based device in which Fusion Nuclear
Science and Technology (FNST) experiments can be performed in the
relevant fusion environment:
1- at the smallest possible scale, cost, and risk, and
2- with practical strategy for solving the tritium consumption and
supply issues for FNST development.
In MFE: small-size, low fusion power can be obtained in a low-Q
(driven) plasma device, with normal conducting Cu magnets
- Equivalent in IFE: reduced target yield (and smaller chamber radius?)
• There are at least TWO classes of Design Options for FNSF:
- Tokamak with Standard Aspect Ratio, A ~ 2.8 - 4
- ST with Small Aspect Ratio, A ~ 1.5
33
Example of Fusion Nuclear Science Facility (FNSF) Device Design Option:
Standard Aspect Ratio (A=3.5) with demountable TF coils (GA design)
• High elongation, high
triangularity double
null plasma shape
for high gain, steady- Challenges for Material/Magnet Researchers:
state plasma
• Development of practical “demountable” joint in Normal Cu Magnets
operation
• Development of Inorganic Insulators (to reduce inboard shield and size of device)
Another Option for FNSF Design: Small Aspect Ratio (ST)
Smallest power and size, Cu TF magnet, Center Post
(Example from Peng et al, ORNL) R=1.2m, A=1.5, Kappa=3, Pfusion=75MW
WL [MW/m2]
R0 [m]
1.20
A
1.50
Kappa
3.07
Qcyl
4.6
Bt [T]
1.13
Ip [MA]
3.4
3.7
2.0
3.0
2.18
8.2
3.8
Beta_N
10.1
5.9
Beta_T
0.14
0.18
0.28
ne [1020/m3]
0.43
1.05
1.28
fBS
0.58
0.49
0.50
Tavgi [keV]
5.4
10.3
13.3
Tavge [keV]
3.1
6.8
8.1
1.5
HH98
0.50
2.5
3.5
Paux-CD [MW]
15
31
43
ENB [keV]
100
239
294
PFusion [MW]
7.5
75
150
Q
T M height [m]
1.64
T M area [m2]
14
Blanket A [m2]
66
Fn-capture
ST-VNS Goals, Features, Issues, FNST Mtg, UCLA, 8/12-14/08
1.0
0.1
0.76
35
Lessons learned:
The most challenging problems in FNST
are at the INTERFACES
• Examples:
– MHD insulators
– Thermal insulators
– Corrosion (liquid/structure interface temperature limit)
– Tritium permeation
• Research on these interfaces must integrate the many technical
disciplines of fluid dynamics, heat transfer, mass transfer,
thermodynamics and material properties in the presence of the multicomponent fusion environment.
• Modeling and Experiments should progress from single effects to multiple effects
in laboratory facilities and then to integrated tests in the fusion environment.
Research must be done jointly by blanket and materials researchers.
36
MHD effects can strongly influence
behavior of melted layers on PFCs during
off-normal plasma events like disruptions
 Melt layers can be generated when large
radiation or particle flux is incident on metal
walls
 Removal of melt layers is a large concern for
the lifetime of metal walls
 MHD effects will result from:
– Induced currents in the melt
• Halo currents closing from plasma edge
• Inductive coupling to plasma current
• Thermoelectric currents
– Induced motion in the melt
• Momentum flux from plasma (plasma wind)
• Thermo-capillary motion
 MHD effects will influence instability
development time and potential for melt layer
removal, and impact convection of heat and
melt layer duration
(Courtesy A. Hassanien, Purdue)
077-05/rs
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Summary
• Fusion is the most promising long-term energy option.
– renewable fuel, no emission of greenhouse gases, inherent safety
• 7 nations are about to construct ITER to demonstrate the
scientific and technological feasibility of fusion energy.
– ITER will have first DT plasma in ~2026
• The most challenging Phase of Fusion development still lies
ahead. It is the development of Fusion Nuclear Science and
Technology (FNST).
– ITER, limited fluence, addresses only initial Stage of FNST testing
– A Fusion Nuclear Science Facility (FNSF) is required to develop FNST.
– FNSF must be small size, small power DT, driven plasma with Cu magnets
• Magnets and magnetic field interactions are a major part of
the magnetic fusion energy system
– Superconducting magnets are used in ITER and essential for Power
Reactors, but Normal Cu magnets with special joints and features are
needed for FNSF.
– LM Blankets are most promising, but their potential is limited by MHD
effects. Innovative concepts must continue to be proposed and investigated.
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